1. Field of the Invention
The present invention relates to a droplet-discharging head, an image-forming device, and a method for positioning head modules of the droplet-discharging head. In particular, the present invention relates to a droplet-discharging head configured such that a plurality of head modules is arranged, an image-forming device, and a method for positioning head modules of the droplet-discharging head. The head modules have nozzle surfaces on which a plurality of nozzles is arranged.
2. Description of the Related Art
By discharging minute ink droplets of ink from the nozzles toward a recording medium, an ink jet recording apparatus is known as an image-forming device for forming an image on a recording medium.
The ink jet recording apparatus is roughly classified into a serial type and a line type. In the serial type, an ink jet head (droplet-discharging head) performs recording while reciprocating in a direction orthogonal to a conveying direction of the recording medium. In the line type, a head performs recording in a state where the head is fixed without movement. The ink jet head mounted on the serial-type ink jet recording apparatus is called a serial head, and the ink jet head mounted on the line-type ink jet recording apparatus is called a line head. The serial-type ink jet recording apparatus has an advantage in that it is possible to record an image on a recording medium with a large area by increasing a distance the carriage moves even when a size of the ink jet head is not increased. In contrast, the line-type ink jet recording apparatus is able to record an image on the entire region of the recording medium without shuttling the ink jet head in a main scanning direction, and thus there is an advantage in that it is possible to perform high-speed recording.
However, in the ink jet recording apparatus, a single image is represented by combining dots which are formed using ink discharged from the nozzles. Accordingly, in order to increase image quality, it is necessary to increase the number of pixels per one image by decreasing sizes of the dots. Hence, in the ink jet recording apparatus, by making the nozzles highly dense, it is possible to increase image quality.
However, in a case of the line head, when the number of nozzles increases, a problem arises in that yield may deteriorate or cumulative pitch error may increase. Therefore, JP2012-16904A and JP2005-329595A propose that a long ink jet head is produced by arranging a plurality of short ink jet heads (head modules).
Even when such a head gets out of order, it suffices that only the defective head module is replaced. Hence, there is an advantage in that an economical operation is possible.
However, a problem arises in that the ink jet head, which is configured such that a plurality of head modules is arranged as described above, is unable to record an image with high quality unless each head module is precisely positioned.
JP2012-930A proposes a method of positioning and mounting the head modules by forming pairs of convex portions and concave portions on the head modules and fitting the convex portions and the concave portions of the adjacent head modules to each other.
Further, JP2008-194972A proposes a method of positioning and mounting the head modules by connecting the adjacent head modules through connecting fittings.